The evolution of Evolution

Most scientists are well-versed in the principles of Darwinian evolution, marked by the vertical transmission of beneficially mutated genes from one generation to the next. Now, a microbiologist and physicist at the University of Illinois-Urbana have hypothesized that horizontal transmission of genetic material may have played an even larger role than previously thought.

Woese believes that along the way biologists were seduced by their own success into thinking they had found the final truth about all evolution. "Biology built up a facade of mathematics around the juxtaposition of Mendelian genetics with Darwinism," he says. "And as a result it neglected to study the most important problem in science - the nature of the evolutionary process."

In particular, he argues, nothing in the modern synthesis explains the most fundamental steps in early life: how evolution could have produced the genetic code and the basic genetic machinery used by all organisms, especially the enzymes and structures involved in translating genetic information into proteins. Most biologists, following Francis Crick, simply supposed that these were uninformative "accidents of history". That was a big mistake, says Woese, who has made his academic reputation proving the point.

In 1977, Woese stunned biologists when his analysis of the genetic machinery involved in gene expression revealed an entirely new limb of the tree of life. Biologists knew of two major domains: eukaryotes - organisms with cell nuclei, such as animals and plants - and bacteria, which lack cell nuclei. Woese documented a third major domain, the Archaea. These are microbes too, but as distinct from bacteria genetically as both Archaea and bacteria are from eukaryotes. "This was a enormous discovery," says biologist Norman Pace of the University of Colorado in Boulder. Woese himself sees it as a first step in getting evolutionary biology back on track. Coming to terms with horizontal gene transfer is the next big step.

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Evidence for this lies in the genetic code, say Woese and Goldenfeld. Though it was discovered in the 1960s, no one had been able to explain how evolution could have made it so exquisitely tuned to resisting errors. Mutations happen in DNA coding all the time, and yet the proteins it produces often remain unaffected by these glitches. Darwinian evolution simply cannot explain how such a code could arise. But horizontal gene transfer can, say Woese and Goldenfeld.

This relatively new thesis helps to better explain the diversity of life on earth. Read the entire article for a fuller explanation.